The analysis of gene expression patterns in normal and genetically altered mouse embryos is a major thrust in each individual project of this Program. To stream-line such analyses and to establish and provide state-of-the-art procedures of embryo analysis, the applicants propose to establish an EMBRYOLOGY CORE FACILITY. The duties of this core are: (1) to determine by in situ hybridization and immunohistochemistry the expression patterns of genes of interest in normal and genetically altered embryos; (2) to interpret these expression data in context of the experimental manipulation that was applied to the particular embryo; (3) to examine embryos with more conventional morphological and histological techniques; (4) to document and archive results of these studies either by conventional photography and/or video-based data processing. Importantly, participation of the researches who have brought in a particular project will be required at all levels. Such an interaction will enhance information transfer and educate members of the program about fundamental aspects of embryo analysis. The core consists of facilities (1) to section embryos, (2) to study sectioned and whole-mount embryos by conventional and confocal microscopy, and (3) to record video pictures that are then computer-processed and stored on disc to be accessible to all investigators of the program. These facilities will be operated by an experienced embryologist/histologist and histology technician, under the supervision of the core director.